1. Field of the Invention
The present invention relates to the repair of high pressure gas or water service pipes which contain a section(s) of leaking or deteriorated pipeline. More particularly, the present invention concerns the insertion of a unique stopper assembly for discontinuing or sealing the flow of the high pressure service into the old section of the high pressure service pipe to be repaired. The stopper assembly further facilitates the insertion of a new, or replacement service pipe within the leaking or deteriorated section, and the pumping of a sealant between the old pipeline and the newly-inserted pipeline. The sealing aspect of the stopper assembly is operated or controlled by a tool means also inserted through the high pressure service pipe, and internally of the stopper assembly. The invention also facilitates pressure testing of the sealed pipeline section prior to returning the high pressure service.
2. Discussion of the Prior Art
Previous servicing and/or replacement of underground high pressure service pipes typically involved excavation of areas adjacent the affected pipe and temporary termination of the flow of gas, either at the point of leakage or at a valve location upstream of the leakage, usually at the connection with the main. Past methods proved to be time consuming and costly, thus it could be appreciated that an alternative method was sought where the replacement of the leaking or deteriorated section could be performed without the need for excavation.
Early improvements involved the insertion of a new pipe section into the old pipe section without the need for excavating, but those early attempts failed to solve higher pressure system sealing. Very early methods involved pumping sealant in between the pipes without the ability to visually confirm a complete filling of the void between the old and new pipes.
Furthermore, prior systems failed to provide a method for pressure testing the repaired section at the seal point before returning the section to service. As these systems typically required the use of a temporary plug in the sealing process wherein the plug was merely removed after sealing stage was completed.
A much more sophisticated service pipe insertion apparatus and method is described in pending U.S. application Ser. No. 08/811,521, to the present inventor. That device solves some of the problems described immediately above, but is limited to use in very low pressure gas systems which are typically held at about six inches of water column pressure. That device provided a hollow nosecone assembly for receiving on one end thereof, the new pipe to be inserted within the deteriorated or leaking old pipe. The nosecone assembly and the new piping was typically fed from the gas meter end, upstream towards the gas main, with the nosecone proper being disposed between the main and the leak. The nosecone assembly included a removable plug that interconnected with the nosecone proper on one end thereof and which received a sealant supply tube on the other end thereof. The sealant supply tube was concentrically received within the newly provided service piping, and thus extended co-extensively to the same location where the new service pipe was inserted (gas meter). At the meter location, a sealant is initially pumped through the sealant tubing, eventually exiting at the end of the plug which was inserted into the nosecone proper. Sealant exit points on the nosecone proper communicate the sealant from the removable plug to the volume of area existing between the old piping and the newly inserted piping. The sealant then reverses its flow direction so that all entrapped air is purged from the volume between pipes, until the sealant again returns to the inlet pumping location. In this way, the entire section of piping from the meter to the nosecone assembly is purged of air and completely sealed. The procedure required a lengthy sealant cure time to pass before continuing, a cured-in-place seal being effected within the nosecone. The removable plug and sealant tubing, being concentrically inserted within the new service piping, is then removed thus re-establishing gas flow from the live side of the assembly into the newly inserted service piping.
The apparatus and method of the present invention on the other hand comprises a modification of the device and method described in U.S. Ser. No. 08/811,521 by providing novel stopping or sealing means for terminating the flow of a higher pressure gas service. Unlike the earlier device which used fins with sealant backing to seal the gas, the device of the present invention utilizes a stopper assembly for creating a two-point sealing of the service line. The apparatus of the present invention also introduces a unique sealant introduction means and methodology for feeding the sealant in between the gap which exists between the old and the new pipes. The present apparatus also provides for pressure testing the system at the seal point, purging air from the system. The present invention does not have a cure time waiting period once the trap door is closed.